1. Field of the Invention
The present invention relates to an ink jet recording apparatus of a dot matrix type in which amounts of electric charges to be given to ink droplets are controlled for producing an inked image in a dot matrix.
The recording apparatus for recording electrical data inputted through a keyboard or the like input device on a recording medium in a form of an image such as a character, symbol or the like are increasingly and widely employed in various and numerous fields in the present age called the age of information. Under the circumstances, various types of the recording apparatus have been developed. Among all, the so-called ink jet recording apparatus in which ink under pressure is jetted as a train of ink droplets from a nozzle incorporated in a recording head thereby to be deposited on a surface of a recording medium such as paper sheet enjoys many advantages. For example, the recording operation is scarcely accompanied by generation of noise due to a lesser number of movable parts used in the recording head. The images such as those of characters, symbols or the like can be sharply recorded with a high contrast. The recording apparatus exhibits a high-speed response to an input signal. Besides, recording can be made even on profiled or three-dimensional surfaces, not to speak of a flat surface, so far as the ink can adhere to them. In view of these advantages, the ink jet recording apparatus is increasingly employed in many and various industrial fields for recording applications.
2. Description of the Prior Art
When an image such as a character, a symbol or the like is to be written or recorded on a surface of a recording medium other than the commonly used recording paper, e.g. on a surface of an article having a three-dimensional configuration by using the ink jet recording apparatus described above, the distance between the surface on which the recording is to be made and the recording head is subjected to variations owing to the fact that the surface state of the article is often not constant, which may cause the characters and/or symbols are recorded to lack overall uniformity in respect of size and shape. Further, there may arise the case where the size of the character and/or symbol is to be altered when occasion requires.
To cope with these situations, the hitherto known ink jet recording apparatus is usually provided with a variable resistor for adjusting the gain of means for amplifying a video signal which is generated for determining electric charge amount given to ink droplets. The variable resistor is manually adjusted by an operator so as to attain a desired recording in consideration of the state or conditions of the recording surface. Such manual adjustment or manipulation is very troublesome particularly when the conditions or state of the recording surface undergoes frequent variations. Additionally, the manual adjustment requires a high skillfulness, as will be explained later.
In the case of the dot matrix type recording apparatus in which the electric charge amount given to ink droplets is controlled, distortion is likely to be produced in the recorded image due to mutual electrostatic interference among the charged ink droplets which are successively emitted from a nozzle of the recording head toward a recording surface. Such distortion has to be corrected, which however requires various complicated circuits and devices, involving a remarkable increase in the manufacturing cost. A typical one of the distortion correcting means is disclosed in U.S. Pat. No. 3,652,757 to V. E. Bischoff issued on Feb. 9, 1971 entitled "GUARD DROP TECHNIQUE FOR INK JET SYSTEMS".